Hi,
On Sat, Jan 23, 2016 at 07:04:54PM +0800, Chen-Yu Tsai wrote:
> Hi,
>
> On Sat, Jan 23, 2016 at 4:31 AM, Maxime Ripard
> <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote:
> > Hi,
> >
> > On Thu, Jan 21, 2016 at 01:26:35PM +0800, Chen-Yu Tsai wrote:
> >> mmc2 and mmc3 are available on the same pins, with different mux values.
> >> However, only mmc3 supports 8 bit DDR transfer modes.
> >>
> >> Since preference for mmc3 over mmc2 is due to DDR transfer modes, just
> >> set the drive strength to 40mA, which is needed for DDR.
> >>
> >> This pinmux setting also includes the hardware reset pin for emmc.
> >>
> >> Signed-off-by: Chen-Yu Tsai <wens@xxxxxxxx>
> >> ---
> >> arch/arm/boot/dts/sun6i-a31.dtsi | 10 ++++++++++
> >> 1 file changed, 10 insertions(+)
> >>
> >> diff --git a/arch/arm/boot/dts/sun6i-a31.dtsi b/arch/arm/boot/dts/sun6i-a31.dtsi
> >> index b6ad7850fac6..1867af24ff52 100644
> >> --- a/arch/arm/boot/dts/sun6i-a31.dtsi
> >> +++ b/arch/arm/boot/dts/sun6i-a31.dtsi
> >> @@ -709,6 +709,16 @@
> >> allwinner,pull = <SUN4I_PINCTRL_NO_PULL>;
> >> };
> >>
> >> + mmc3_8bit_emmc_pins: mmc3@1 {
> >> + allwinner,pins = "PC6", "PC7", "PC8", "PC9",
> >> + "PC10", "PC11", "PC12",
> >> + "PC13", "PC14", "PC15",
> >> + "PC24";
> >> + allwinner,function = "mmc3";
> >> + allwinner,drive = <SUN4I_PINCTRL_40_MA>;
> >> + allwinner,pull = <SUN4I_PINCTRL_NO_PULL>;
> >> + };
> >> +
> >
> > Is that reset pin optional?
> >
> > If so, I'd prefer it to be a separate node, like we're doing for the
> > SPI chip selects for example.
> >
> > It allows more reusability between different devices without declaring
> > new nodes.
>
> All eMMC devices have a reset pin. The MMC standard specifies this as
> one way to reset the card, others being a special reset command, or
> powering the card off. It also notes a state when the card will not
> accept commands, and will require a power cycle or asserting the reset
> pin.
>
> I assume all designs would route this pin. The FEX files also have this
> pin included by default.
I was more concerned about the case were you'd have a 8bits bus
without an emmc. But I guess that can't happen, since all SD cards are
using a 4 bits width anyway.
I'll apply this patch.
Thanks!
Maxime
--
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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